Zcash NU7 goes live this week: 25-second blocks and a 40% fee share for miners
Zcash is set to activate its NU7 network upgrade at block 3,543,405, expected on the night of November 5 to 6. From that block on, the chain targets one block every 25 seconds instead of every 75. It is the biggest protocol change ZEC miners have faced in years, even though the mining hardware itself will not notice a thing.
How rewards change
There will be three times as many blocks, each paying a third of today's subsidy, so the amount of ZEC issued per day stays the same. The four-year halving schedule and the 21 million ZEC cap are untouched; halving intervals measured in blocks are simply tripled. The real novelty is fees. Under the Network Sustainability Mechanism, 60% of every block's transaction fees go into a reserve and the miner keeps only 40%. Part of that reserve will later be paid back out through block rewards, but on mainnet that only starts at height 8,939,664, years from now.
What miners need to do
- ASIC on a pool. Antminer Z15 and Z15 Pro owners do not need new firmware, since the Equihash algorithm stays the same. Just check that your pool has confirmed it is NU7-ready. Payouts should get smoother because blocks arrive three times as often.
- Solo miners and pool operators. Nodes must run Zebra 7.0.0 before the activation height. After NU7, outdated nodes follow a separate chain and upgraded peers disconnect them. The first start migrates the state database to a new format, so the developers suggest backing up the state/v28 folder first.
- Block templates. Only the time field in getblocktemplate is mutable now. Do not edit the transaction set or the previous block yourself; request a fresh template, and make sure the coinbase claims only the miner's 40% of fees.
- Wallets. Version 4 transactions become invalid at activation, and any funds still sitting in the old Sprout pool become unspendable. Move them before the switch.
The Zcash Foundation lists every change in its Zebra 7.0.0 announcement. This release is supported for only 8 weeks instead of the usual 12, so expect another node update soon after the upgrade.